Hello,
Its been a while since I last posted, very busy with work/car. Unfortunatly, I have a problem. I'm currently rebuilding my 355. The crank is installed, main caps are torqued (4bolt main). I am now putting in the pistons and i've run into a problem... I have 7 pistons installed, basicly, I instaleld 7, and went to supper... when i came back I tryed to turn the crank so the last pistons could be installed, however, this time i can't even turn the crank! It is VERY stiff.

I have no clue whats going on... It wasn't like this when I left it and no one was at it. Everything is very well lubed and nothing seems to be hitting anything.

Does anyone have any ideas? This seems very strange...

 

Should break loose at about 20 ftlbs w/a torque wrench. No way I could turn mine by hand even with 4 pistons installed, unless you're using low tension rings or something.

Once you "bump" it to get it going, it should be easier until you stop it again. Normal.

 

Check that none of the pistons/rods are installed backwards.

 

Which way are the rods suppose to be in there? I have the "lips" facing toward the outside of their journals...

 

The tangs on the bearings should face away from the cam.

 

Sorry, I don't quite understand what you mean by "face away from the cam"...

Thanks

 

One side of the rod faces toward the cam, the other side faces toward the oil pan & the ground (or toward you, if it's still on the stand upside down).

The bearing tangs for both the rod half and the cap half of the bearing should be on the same side, and that should be the side that is away from the cam; i.e. the side of the rod visible to the builder.

Crank journals may have a radius where the rod pin meets the throw. Rod bearings ARE NOT symmetrical; they are designed such that the edge of the bearing that's supposed to face toward its neighboring rod, is wider than the edge that's supposed to be against the throw. If you put the piston-rod assy in backwards (or, if the piston is installed on the rod backwards, and thus the rod is turned around backwards on the piston), then the wide edge of the bearing will ride up on the radius on the crank, and the 2 rods on that pin will be forced together HARD, and the crank will be very difficult to turn.

A fully built short block should take about 30 ft-lbs to turn. Any more than that, something isn't put together right.

 

Thanks a lot. I understand now.. hmm.. that gets me thinking..

I'll check out after I get off work..

 

I should mention, that not all cranks are ground with a radius, and not all rod bearings are asymmetrical like that. However, typical performance-oriented parts are made that way. Not stock (or reground stock) cranks, usually, or "replacement" bearings; but the more racing-type ones are.

You should be able to tell right away which ones are the problem. Look at the rod side clearance. The rods should slide completely freely from side to side on the crank journal, and each rod should have .015" of free play, more or less. (about .008" - .020" is typical and acceptable, with about .012" - .016" ideal). If the rods don't slide, and under no circumstances can you get your feeler gauge in between the 2 rods on one journal, then that's the one(s) that might be put together backwards.

 

awsome... I'll take a look at that. Great info.

I gotta say, its nice workin on the ol 'bird again.

 

ok, I ran down and checked it on my lunch break...

They all seem to be in correctly, however I still cannot turn it..

Is it possible the lube has "settled" in one spot and its just tough to break lose?

 

Can you turn it in either direction? Nothing's interfering anywhere?

 

No, It won't turn either way. And nothing is in the way...

Funny thing is, I can't move the rods at all... yet all the they are in the right way...

I really don't understand this.. I'm sure it wasn't that hard to move before it sat for an hour or two.. I can't even budge the thing now..

 

You can't move any of the rods at all??

That's not right. Sounds like it's time for a mic and a bore gauge. Time to check your crank journal diameter, and the inner diameter of your bearings.

 

nope.. when there is two rods on the crank I cannot move it. (obvisoly, I can when theres only one)

The crank and rods both just came back from the machine shop. The crank is actually a replacement. The rods where resized. Also, I just finished plastigauging(i know its not extremely accurate, but its not bad) the rods and mains.. they all checked out. I'll take a good look tonight, at it since i was rushed earlier... if it comes out bad i'll be taking another visit to the machine shop.

So your saying I could be able to just wiggle(.008"-.02") the rods when there torqued on and lubed?

 

Correct.

There should be .002" or so of clearance between the bearings and the crank, and .015" or whatever between the 2 rods on a journal; and the wrist pins should be free to slide endwise in the piston. So you should easily be able to slide the rod front-to-rear on the crank.

If you can't, then something's wrong. Mismatched rod caps, something backwards, parts the wrong size, something is wrong.

 

Yes, there should be a small amount of side play.

 

Ok, I just checked.. It looks like all the rods/pistons are put in right... and I know that the crank turned freely with no pistons installed.
I cannot wiggle the rods(but I know the wrist pins slide easily) nor turn the crank and I cannot fit any size feeler gague in there.

Anyone have any advice on what to do? I guess calling my machine shop is about all I can do..

 

Take one rod off of one crank journal, and see if the other rod on that journal can then move freely. Put that one back on, and take the other off; check again. Check all 8 that way. Inspect the edges of the rod bearings VERY CAREFULLY, look for any sign that the edge has been forced hard against the crank radius.

See if you can turn the crank if you loosen all 8 rod caps.

Something is clearly wrong. Not put together right somewhere.

 

Since you were able to get the 7th one installed I'd take it back out and see what's in a bind.

If it wasn't the last one you installed you would have noticed it before, probably???

 

if all else fails you might have to remate the rods and caps. i had the same problem on the last motor i built. got down to number 7 and the crank wouldn't budge. it took some time and patience remating the rods and caps, but i finally found a combination that worked. better that than to risk damaging your crank. good luck RR

 

Were the rods resized when you put in new bolts? Are the rod caps on the same rods they were on originally? Did you maybe get the wrong set of rod bearings... like, for a differently ground crank than what you actually have?

 

Ok guys, this is what I found out..

Ok, theres pretty much no clearence between rods.. The rods appear to be put in the right way... It is a standard crank, with resized rods and I am using standard bearings.

Also, there is oil behind the bearing... Is this normal? I can say that when I put it in it was VERY dry and clean.

Thanks guys.. I'm going to call the machine shop tomorrow.. see what they think.

 

Measure the width of the rods, and the "length" of the journal on the crank. 2 rods should add up to about .015" less than the "length" of the crank journal.

If you don't have a set of calipers, get one; it's probably THE most essential engine building tool. Given the level of tolerance you're looking at here, you don't have to spend alot of money or anything. A cheap one from Sears will do just fine. Or, go to McMaster-Carr and look at their part # 2289A42.

 

Good stuff, I will do that. I have a nice mic, but buying a caliper is somthing thats always been on the back burner...

What about the oil behind the bearing, is that normal? I've always been told that it should be dry to prevent the bearing from spinning...

 

It usually ends up back there whether you put it there or not; in any case, it will certainly be there within 10 seconds after the motor initially cranks up.

Having some oil there won't make the bearing spin, and not having it there won't keep it from spinning. The tangs on them are supposed to do that.

That said, I wouldn't PUT it there; you should assemble them dry, so that they "crush" into the rod and cap properly. But once that's done, it's a non-issue.

 

Alright guys I found out what it is.. sorta wishing I hadn't.

I ended up checking every rod seperatly and measuring the torque. They all were ok untill I got to number 5.. it just won't spin very easy.. so I took it apart to find that the crank has a coupe little tiny gouges in it and it was hooking in the bearing, tearing it to crap.

I have NO idea how this happened, and I don't when it happened. I used thoughs little rod bolt covers so this wouldn't happen. However, it does look like a rod bolt did the work. I am so sure it couldn't have been me though, because I took such care and theres no way the rod bolt it THAT hard to gouge it.

I feel so cheated as this WAS a replacement crank... anyone have any ideas? is there anyway to fix this besides a reground/replace?
I'll have to deal the machine shop I bought it from on Monday.. they did the polishing too, if it was there before you think they would have noticed though.

 

Well at this point, it just kind of is what it is, so it's hardly worth worrying too much about who did it. You'd be surprised how easy it is to nick the crank with a rod bolt though.

But, think about this: the shop didn't have any rod bolts anywhere near the crank, now did they? So how could they POSSIBLY have done it?

But, it's probably no big deal at all, since you caught it. You can file / grind / sand the nick down, if it's not too large. If you can get it to the point where you can't feel the raised parts of it with your fingernail, then it won't matter.

If the bearing is gouged, you should replace that. That's cheap and easy.

I use pieces of that clear plastic tubing like aquarium hose on the rod bolts to keep that from happening.

The VERY LAST THING you should be doing, right before stabbing a piston in, is cleaning the rod journal with a lint-free towel of some kind (coffee filter is good) followed by some spray can carb cleaner or starting fluid. Same for the rod and the cap and the piston skirts and ring lands; you don't want any drt there either. You should have the rod bearings sitting in a little can or something of clean fresh lacquer thinner. You should have some rubber or plastic gloves on so you don't get fingerprints on the bearings. Put a few drops of oil on the journal, from a squirt-type oil can so you don't have to touch anything. Take a pair of bearing halves out of the thinner, let them air-dry, put them in the rod and the cap. Put a few drops of oil on the journal, from a squirt-type oil can so you don't have to touch anything, and install the piston in the bore. I use either ATF or real light-weight synthetic oil as bearing lube; 2-stroke oil on the rings.

 

Good info sofa.

To be honest I'm really not worried with who did it, I was just frustrated at the time.

The little gouges arn't that deep so i think I get the "lip" of it so its smooth. Only time will tell. Your right though, it is better that I catch it now.

 

Was this nick on the crank journal? I have a place on my #1 main journal that is nicked and I can feel it with my fingernail.

How can you lightly polish a crank at home? 0000 Steelwool?

 

I would think something like emery cloth might be better.

 

A couple points to note after reading the thread;

a.) Do not mix up rod caps. They are machined to a particular rod and should never be mixed up.

b.) Always check your bearing clearances. Invest in a good dial bore gauge and a micrometer that reads to .0001". Plastigauge will get you close if your building a stock motor but for a performance build it's not going to cut it.

c.) Dial verneer calipers are not suitable for measurements finer than .001"

d.) Rod side clearance is very important yet often overlooked. Not enough and you end up with excess friction, heat and poor oiling. Too much and you end up with nothing more than an internal oil leak and loss of pressure. Measure the thickness of two paired rods (1&2, 2&3, 3&4 etc.) then measure the width of the corresponding journal on the crank. Take the difference of the two and you have your clearance.

e.) Clean clean clean. This should go without saying. Keep the parts clean, keep your hands clean, keep your shop/work area clean.

f.) Lubrication is your friend. No metal parts should ever touch one another without some sort of lubricant. Oil or loctite on the threads and oil inder the heads of bolts. Proper assembly lube on any aftermarket bolts or studs as reccomended by the manufacturer. If you're mocking up the engine prior to final assembly, use oil on the bearing surfaces. For final assembly use a high quality assembly lube. Pison skirts/cylinder walls get a coating of WD40, or oil depending on what kind of surface finish has been given to the bores and also what kind of rings are being used.


BTW you can touch the bearings with your hands, it wont hurt anything as long as you're clean. If the oils in your skin are able to hurt the bearings, you've got bigger problems.